Mathies et al. (U.S. Patent Publication 2004-0209354) describes a microfluidic structure comprising: a first surface including a pneumatic channel; a second surface including a fluidic channel; and an elastomer membrane located between the first and second surfaces such that the application of a pressure or a vacuum to the pneumatic channel causes the membrane to deflect to modulate a flow of a fluid in the fluidic channel.
Fluid flow in a fluidic conduit of such devices can be regulated by a diaphragm valve in the conduit that comprises a valve seat on which the elastomer membrane sits. When in contact with the seat, the elastomer membrane blocks fluid flow across a fluidic conduit. When out of contact with the seat, a passage exists that allows fluid communication across the valve.
Anderson et al. (Nucleic Acids Res. 2000 Jun. 15; 28(12):E60) describes a plastic device held together using ultrasonic welding or adhesives.
In certain embodiments the elastomer membrane comprises a sheet of polydimethylsiloxane (PDMS) sandwiched between two glass layers. The elastomer membrane normally sits on a valve seat and is displaced from the valve seat by the application of negative pressure to the opposing surface of the elastomer. Typically, the elastomer membrane seals the valve through contact or bonding with the surface of the fluidic and pneumatic layers, and the valve functions as long as the elastomer membrane does not become stuck to the valve seat or other exposed surfaces or the device de-laminates as a result of insufficient bonding between the elastomer layer and the contacting surfaces of the fluidic and pneumatic layers.